Fluorescent lamp coating machine



June 30, 1959 Filed Aug. 7. 1957 J. w. FULTON ET AL 2,892,440

FLUORESCENT LAMP COATING MACHINE 4 Shee ts-Shet 1 a, lnveni'ofs: John W. FLilFlTOTI,

Robev t AKuebLeT by MW Their Attrorne9 June 1959 J. w. FULTON ET AL 2,892,440

FLUORESCENT LAMP COATING- MACHINE 4 Sheets-Sheet 5 Filed Aug. 7, 195'? Inven TOT'SE v John WiFukton, Rober lr AKuebLer',

' 109 I 6 P A ,Th'eiv A b lrovnes.

June 1959, Y J. w.- FULTON ET AL 0 FLUORESCENT LAMP COATING MACHINE v v l L56 W 5 w-zfzow Spa-0) Low Nap/m1 BAC/(W/JED F 2 4 0 55 550 SPEED 1 P044 Pofi E 3 A WWW C- Inven trovs.

M0702 EC-a John \(viFuL lron, E M RObeFt KuebLev,

2 bg JAM Their A tdrovngg.

United States Patent FLUORESCENT LAMP COATING MACHINE John W. Fulton, Chardon, and Robert A. Kuebler, Cleveland Heights, Ohio, assiguors to General Electric Company, a corporation of New York Application August 7, 1957, Serial No. 676,812

11 Claims. (Cl. 118-56) This invention relates to the manufacture of reflector or directional fluorescent lamps of the elongated tubular kind wherein part of the envelope is coated internally with a reflective coating in a longitudinally extending band. The entire envelope is coated internally with a luminescent material or phosphor but the light output is concentrated by the reflector in the non-reflectively coated or window portion. The invention is particularly concerned with a machine for applying the reflective band in such lamps.

In order to produce a reflector fluorescent lamp which is an attractive product, it is necessary to provide a refiector coating of even thickness and having regular and straight edges. Unevenness or irregularity of the edges are accentuated by the contrast between the coated and noncoated portions of the lamp during operation.

In the first manufacture of reflector fluorescent lamps, the practice has been to coat the entire internal surface of the envelope with the reflective material, and thereafter to remove the reflective coating from the area intended as the window. Such removal was effected by scraping or rubbing after the coating suspension or paint had dried, thereby producing dust which was diflicult to remove entirely and reduced the quality of the product. The edges tended to be wavy or scalloped if a brushing technique was used, and also the method was wasteful of the reflective material consisting generally of titania or titanium dioxide, inasmuch as the material brushed or scraped off was scrapped.

The object of the invention is to provide a new and improved machine for applying a coating or paint to a selected interior area or are extending in a longitudinal hand through a tubular envelope.

Another object is to provide a machine for automatically applying a coating to a portion of the interior of a lamp envelope and applying the method described and claimed in copending application Serial No. 676,813 of Milton E. Patterson, Kenneth E. Luna and William E. Ishler entitled Fluorescent Lamp Coating Method, filed of even date herewith and assigned to the same assignee as the present invention.

A more specific object of the invention is to provide a machine for applying to the interior of a tubular fluorescent lamp envelope a reflective coatingv extending over a selected are of the cross section and having well defined straight and regular edges without further processmg.

In accordance with the invention, the desired reflective area is applied to the interior of a tubular envelope by a machine which deposits a longitudinally extending pool of coating suspension or reflective paint in the horizontally supported bulb, and thereafter rocks the envelope about its longitudinal axis to cause the pool to extend over the desired are or section of the envelope.

In a preferred machine embodying the invention, the envelope is supported in a rigid semi-cylindrical cradle into which it is pulled down by a vacuum. The vacuum pull-down causes the envelope to conform to the cradle and overcomes any minor bowing of the envelope normally encountered. The pool of coating suspension is introduced by means of a long nozzle which is inserted into the envelope and which releases the suspension from its end as it is withdrawn. Thereafter the cradle is rocked back and forth through a suitable angle less of course than 360 for spreading the pool to achieve the desired angular width or are of reflective coating. Preferably the roll of the cradle is slowed down before reaching the limits of arc and it is stopped momentarily at the limits in order to allow the coating suspension to creep up into a straight line or edge.

For further objects and advantages and for a detailed description of a preferred embodiment of the invention, attention is now directed to the following description and accompanying drawings. The features of the invention believed to be novel will be more particularly pointed out in the appended claims.

In the drawings:

Fig. l is a cross section of a fluorescent lamp showing the disposition of the internal reflector and phosphor coatings. V

Fig. 2 is a pictorial illustration of a flow coating machine embodying the invention suitable for the manufacture of eight feet long reflector fluorescent lamps.

Fig. 3a and b together are fragmentary side elevation of the machine with portions cut out in order to foreshorten the figure.

Fig. 4 is a vertical section through the coating suspension reservoir and pump therefor.

Fig. 5 is a plan view, partly in section, of the nozzle and pump for the coating suspension.

Fig. 6 is a transverse section through the cradle and axle of the machine taken along line 66 in Fig. 3a and showing the slow-down cams and associated switch.

Fig. 7 is a similar transverse section taken along line 77 in Fig. 3b and showing the roll limit cams and associated limit switches.

Fig. 8 is a similar sectional view taken along line 8-8 in Fig. 3b and showing the center stop cam and associated limit switch.

Fig. 9 is a fragmentary end view of the machine seen along line 99 in Fig. 3b and showing the cradle centering cam and associated parts.

Fig. 10 is a schematic diagram illustrating the control system for the machine.

The type of lamp which the machine is used to manufacture is illustrated in section in Fig. 1. The cylindrical glass envelope 1 is coated internally throughout its lower portion, somewhat in excess of a half section, with a lightreflective coating 2 of a suitable finely ground material such as titanium dioxide. The entire interior of the envelope, including the reflectively coated lower portion, is further coated with a luminescent material or phosphor 3. The phosphor may be any of those commonly used for fluorescent lamps, for instance an alkaline earth halophosphate. The ultraviolet 2537 A. radiation produced by the mercury vapor discharge through the envelope causes visible light to be produced throughout the entire phosphor coating. However, that light produced by the phosphor overlying the reflective titania coating is reflected back into the envelope until it escapes through the A-frames 6 serving as legs. The lamp envelopes are 2,892,440 I V e V accommodated in a semi-cylindrical cradle 7 attached to a horizontally extending hollow shaft 8 by a series of welded vertical plates 9. Hollow shaft 8 is journalled at both ends in bearings 11 and at the center in a half pillow-block 12, these parts being attached to transverse plates clamped to I-beam by bolts 13. Shaft 8 is oscillated back and forth by a reversible electric motor 14 through a solenoid controlled clutch 15 and reducing gear The illustrated machine can process a single 8 foot lamp envelope at a time or two 4 foot envelopes simultaneously, one such 4 foot envelope being illustrated at 1 in Fig. 2. Elongated tubular glass envelopes are inevitably bowed to a minor degree and it is necessary to straighten them out during the coating operation to insure that the edge of the coated area formed by the pool of coating liquid is straight and uniform. To this end, cradle 7 is rigidly constructed of sufficiently heavy material and it is provided along its edges, both longitudinally and endwise, with partly recessed rubber O-tubing 17 to form a sealed space under each four foot section of envelope (Figs. 3a and 6). During the coating operation, sealed space 18 is evacuated in order to pull the lamp envelope down tight into the cradle, thereby correcting any bowing of the envelope. Vacuum is applied to each section of the cradle through tubes 19 from hollow shaft 8, and to shaft 8' through a slip coupling 21 at its left end (Fig. 3). A source of rough vacuum is connected to supply tube 22 of coupling 21 through a solenoid controlled valve V-1 (Fig.

The deposit of the pool of coating suspension in the lamp envelope in the case of an eight foot lamp is made by a pair of reservoir and nozzle assemblies 23, 23 mounted on carriages 24, 24' which roll on the edges of the I-beam flanges. If two four foot lamps are being processed simultaneously, both reservoir assemblies will likewise be used but if only one four foot lamp is being processed at a time, one reservoir assembly may be left disconnected.

As best seen in Fig. 3a, carriage 24 comprises a top plate 25 to which are fastened dependent vertical side plates 26. On the side plates are mounted grooved upper rollers 27 which ride on the top flanges of the I-beam to support the carriage. The lower rollers 28 are attached to L-shaped brackets 29 which are pivotally mounted on the side plates and biased by springs 31. The lower rollers riding on the underside of the I-beam flanges stabilize the carriage and maintain it level. Carriage 24' at the opposite end of the frame, that is at the right end in Fig. 2, is similar to carriage 24 in respect of the parts so far described.

The carriages 24, 24 supporting the reservoir and nozzle assemblies are normally fully drawn apart, that is to the outer ends of the I-beam frame. In this position, the long nozzles 32, 32' are entirely clear of the cradle and of the envelope or envelopes supported therein. Lamp envelopes may then be loaded into the cradle without interference, the cradle being at such time centered in its vertical position as illustrated in Fig. 2. After the application of vacuum to the cradle in order to straighten out any bowing in the lamp envelopes, the carriages are caused to move together in unison so that the long nozzles penetrate the lamp envelopes until the nozzle end caps 33, 33 practically meet in the center. The carriages then move apart to return to their original position and the coating suspension is issued from the nozzle end caps during the withdrawal.

The movement of carriage 24 is effected through a hydraulic ram 34 (Fig. 3a) fastened to frame 5 and having a piston 35 actuating a rod 36 fastened to member 37 of the carriage. Pressurized oil may be admitted to supply tube 38 of the ram to cause the forward movement of the carriage for the insertion of the nozzle, and to supply tube 39 to cause the outward movement for the withdrawal. The other carriage 24' is driven in unison with carriage 24 by means of an endless chain 41 extending between sprockets at both ends of frame 5. The sprockets are located under guard covers 42, 42' shown in Fig. 2, and one sprocket 43 is shown in Fig. 3a. The carriages are connected to opposite sides of the chain so that as carriage 24 is driven by the hydraulic ram, carriage 24 follows in unison. The supply of pressurized oil to the hydraulic ram supply tubes 38, 39 is controlled by solenoid operated valves V 2, V-3 (Fig. 10).

The reservoir and nozzle assemblies 23, 23' each comprise a cylindrical tank or reservoir 44 for holding a suitable quantity of the reflective coating suspension. A vertical air motor 45 mounted above the reservoir and to which compressed air is admitted through a supply tube 46, drives a four vane impeller 47' by means of a vertical shaft 48 extending through a concentric tube or well 49 in the reservoir. Impeller 47 is located in a housing 51 on the underside of the reservoir and the housing communicates with the reservoir through apertures at 52 in central well 49. Coating suspension is thus admitted centrally into the impeller housing and it is driven by centrifugal force into outlet channel 53 in the housing block. Channel 53 leads the fluid into the annular space between outer pipe 32 of the nozzle and concentric inner tube 54 through a mounting block 55 attached to housing 51. The reservoir and housing are supported on top plate 25 of carriage 24 by means of a sturdy bracket 56.

The reflective coating suspension which may consist of titanium dioxide in an organic vehicle including butyl acetate and a nitrocellulose binder, must be kept in continuous circulation in order to prevent the titanium dioxide from settling out. The how of suspension through the reservoir and nozzle assembly is indicated in Fig. 5 by the arrows. It will be observed that impeller 47 at all times forces the suspension out through channel 53 and through the annular channel between outer nozzle pipe 32 and inner tube 54 towards the end of the nozzle. The outer pipe is terminated by a blind end cap 57 screwed thereto, and the inner tube is terminated by a plug 58 which makes a sliding fit in the end cap. Inner tube 54 is provided near its forward end with a restricted aperture 59 which serves as a by-pass allowing the coating suspension to flow back through the inner tube 54 as indicated by the arrows.

Due to the restricted size of aperture 59 by comparison to the cross section of the annular channel between inner and outer tubes, there is a constant pressure head maintained in the annular channel tending to force fluid through small passageway 61 extending through plug 58 into blind cavity 62 formed by the end wall of the cap and the forward wall of the plug. When fluid is to issue from the nozzle during the withdrawal stroke up to the point where the end cap reaches the end of the lamp envelope, cavity 62 is vented by uncovering lateral aperture or port 63 in the wall of the end cap. For ease of illustration in Fig. 5, port 63 has been shown as being in the side of the end cap. In fact, port 63 is located on the underside of the end cap in the same relative axial position as illustrated; this allows the fluid to drop directly to the bottom of the lamp envelope without splashing on the sides. Normally port 63 is covered by plug 58; to open the port, plug 58 is withdrawn, that is moved to the left as illustrated in Fig. 5, by an axial movement of the entire inner tube 54. The inner end of the tube is connected into a throttling valve 64 located within bracket 65. A pneumatic cylider 66 is attached to the outer end of bracket 65. and is mechanically linked to the throttling valve by a connected rod 67. The supply of pressurized air to the pneumatic cylinder is controlled by a solenoid operated air valve V-4 (Fig. 10). The return of fluid from the throttling valve into reservoir 44 occurs upwardly through pipe 68 and then over and down through a portion which extends through a slot 69 in top cover 70 of the reservoir. Slot 69 allowsv the axial movement of the throttling valve necessary for opening the port in the end cap of the nozzle without interference.

, In order to obtain a sharp and even edge to the reflectively coated area of the envelope, it is desirable to roll the envelope slowly just prior to the limits of roll and to hold it stationary for a short interval of time at the limits. This allows the pool of coating suspension extending the length of the envelope to creep slowly up to its final position, thereby achieving a smooth and even edge. It is desirable to avoid both streaks and drapes in the reflector coating. The term streaks is used to describe the especially heavy lines due to excessive flow of coating into the center of the bulb while in the horizontal position. The term drapes is used to describe those defects resulting from excessively fast drying, especially along the edges of the coating pool in the horizontal position of the envelope. The term drapes is also used to describe those defects resulting from excessively fast settling of the coating when the lamp is removed from the flow coating machine and held vertically in a drier. To avoid such defects and in order to produce a smooth coating, it has been found desirable to roll the envelope a number of times from limit to limit. The preferred technique consists in starting the envelope in its vertical position, and then providing successively a halfroll backward to one limit, a full roll forward to the other limit, a full roll backward to the one limit again, a full roll forward to the other limit again and then a half-roll backward to center the envelope in its vertical position. In order to speed up the processing of envelopes as much as possible, a high rate of rolling is provided until just prior to the limit when the rate of roll is slowed down. At the limit itself, the rolling motion is temporarily stopped as previously explained.

.The flow coating machine provides this desired mode of operation by means of a control system to be more fully described shortly by reference to Fig. 10. The operation of the control system, however, is governed by a number of limit switches which come into play at various times during the rolling cycle. The first of these switches is LS-S shown in Figs. 3a and 6. This switch is normally open and its armature or actuating roller 71 is positioned for engagement by either of two cams 72, 72' secured by nuts 73, 73' on shaft 8. The angle of roll at which cams 72, 72' actuate limit switch LS-S to slow down the roll motor is adjusted by turning the. cams. relative to shaft 8.

The limits of roll of the cradle are determined by the actuation of limit switch LS-6 for the backward roll and 1.8-7 for the forward roll (Fig. 7). The push button armatures 74, 74' of these switches are actuated upon engagement by cam members 75, 75 extending from split clamps 76, 76 fast on shaft 8. The clamps are adjustable on the shaft to vary the angle of roll whereby to determine the width or angular spread of the reflective band applied to the envelope.

On the final half-backward roll, the roll motor is stopped about the time when the cradle reaches its vertical position through the operation of limit switch LS-8 (Fig. 8). This switch has its operating roller or armature 77 riding on a cylindrical surface 78 defined by a pair of clamp members 79, 79 fast on shaft 8. The switch is actuated when the roller enters depression 81 in the cylindrical surface.

To assure positive centering of the cradle and also in order to lock it centered, there is provided a centering cam 82 on the end of extension shaft 83 projecting from reduction gear box 16 (Fig. 9). Shaft 83 is mechanicatly clamped to main hollow shaft 8 and turns with it. On the underside of centering cam 82 corresponding to the vertical position of the cradle, there is provided a rounded V-shaped notch 84 adapted to be engaged by a roller 85 journalled on the upper end of member 86 welded to lever 87. Lever 87 is pivotally mounted at 88 on a bracket 89 fastened to the side of I-beam frame 5. For centering the cradle and also in order to hold it locked in its vertical position during the loading of the lamp envelopes and during the insertion and withdrawal of the nozzles, lever 87 is swung up from its lowered position illustrated in Fig. 2 into that illustrated in Fig. 9 wherein roller has penetrated notch 84 in centering cam 82. If the cradle is not perfectly centered in its vertical position, the roller will engage the sloping sides of the notch and bring the cradle back into its vertical position. Lever 87 is forced up by a rod 90 operated by a pneumatic cylinder 91 (Fig. 3b) under the control of solenoid operated valve V-5 (Fig. 10) for regulating the supply of compressed air thereto. At the same time as the centering mechanism is operated, roll motor 14 is disconnected from reducing gear box 16 by a solenoid operated motor clutch 15 operated by winding MCW (Fig. 10).

The automatic operation of the machine to perform the functions which have been described is achieved through a control system schematically illustrated in Fig. 10. Automatic rotary indexing switch 92 illustrated therein and its associated relays are contained in control box 93 (Fig. 2). Line switch S-la, S-lb along with fuses Fa, Fb for connecting the system to the 115-120 volt A.C. supply at terminals La, Lb are contained in switch box 94 (Fig. 2). Push-button start switch S-2 and stop switch 8-3 project from a wiring box 95 on the side of frame 5 and start switch 8-2 is also duplicated as a foot-operated pedal switch 96 for added convenience. In the sequence of operations of the control system, start switch S-Z begins the cycle of operations after the lamp or lamps have been loaded into the cradle. The cycle may be stopped at any time before its completion by depressing stop switch 8-3. When start switch 8-2 is closed, a circuit is completed across line terminals La, Lb through normally closed stop switch S-3 and holding relay winding RW-l. Holding contacts RC-l close and the circuit is completed from line terminal La to conductor 97, thereby energizing the three banks of automatic indexing switch 92, namely the index control bank, the power control bankand the centering control bank. The automatic indexing switch has 12 positions and is at rest in position l'when start'switch 8- 2 is closed. The completion of a circuit in the appropriate level of the index control bank will cause indexing coil 98 of the switch to be energized through its rectifier 99 whereupon the switch steps to the next level. When conductor 97 is energized, solenoid controlled valve V -1 is operated by winding VW-l through bridge rectifier 100. The lamp envelope becomes seated in the cradle and the vacuum developed therein causes a limit switch LS-1 to close. The indexing switch thereupon steps to position 2. Relay winding RW-3 then becomes de-energized and relay contacts RC-3 which had been open up until now assume their normally closed position. A holding circuit comprising contacts RC-l held closed by winding RW-1, and normally closed contacts RC-3, is completed around start switch 8-2 which may now be released without interrupting the cycle.

Upon movement of the automatic indexing switch to position 2, relay winding RW-4 became energized, cans ing contacts RC4 to close. This energizes solenoid VW2 operating valve V-2 controlling the supply of pressurized oil to hydraulic ram 34 for the insertion of the nozzles into the lamp envelope. When nozzle 32 has penetrated the lamp envelope to its full extent, limit switch LS-Z is closed by inclined cam member 101 attached to one of side plates 26 of carriage 24 (Fig. 2). The automatic indexing switch now steps to position 3 and relay winding RW-S becomes energized causing con tacts RC-5a and RC-Sb to close. The closure of-con tacts RC-5a energizes solenoid VW-3'causing the operation of valve V3 controlling the supply of pressurized fluid to the hydraulic ram for the withdrawal of the nozzles. At the same time, the closure of contacts RC-Sb causes the energization of solenoid VW-4 through normally closed limit switch LS-3 to open valve V-4. Valve V-4 operates air cylinders 66 to open ports 63 at the ends of thenozzlesallowingthe coating suspension to flow into the lamp envelope. When nozzle 32 has been withdrawn to the point where it has reached the outer end of the lamp envelope, inclined cam member 102 on vertical plate 26 of carriage 24 causes normally closed limit switch LS-3 to open. This opens the circuit of solenoid VW-4 and stops the How of coating suspension from the nozzles. Further withdrawal movement of the nozzle assembly causes inclined cam member 103 to close limit switch LS-4. The automatic indexing switch thereupon steps to position 4 and the carriages come to rest.

A pool of coating material now extends longitudinally along the bottom of the lamp envelope which may now be rocked to spread the pool circumferentially. In the first three positions of. indexing switch 92, relay winding RW-S in the centering control bank was energized and maintained normally closed contacts RC-8a open and normally open contacts RC-Sb closed. When contacts no-sa are open, solenoid winding MCW is not energized by bridge rectifier 104 and motor clutch 15 is open so that roll motor 14 is disconnected from the reducing gear box. When contacts RC-8b are closed, solenoid winding VW-5 is energized and maintains valve V-5 open; this admits compressed air to air cylinder 91 (Fig. 3b) and locks centering cam 82 with the cradle vertical. Starting at position 4 of the indexing switch, relay Winding RW-8 isno. longer energized; the cradle is thereby unlocked and clutch is closed so that roll motor 14 may go into operation.

The initial movement of the cradle is a half-backward roll from the vertical to the back limit. The closing of relay winding RW-6 causes contacts RC-6a and RC-6b to close so. that thyratron motor control 105 operates motor 14 in its reverse direction. At this time, the motor. control is regulated by normal speed potentiometer P-l through normally closed contacts RC-2a and R041). Prior to the limit of backward roll, limit switch LS-S is closed by cam. 72 (Fig. 6) causing the energization of relay windingRW-Z. Relay contacts RC-2c and RC-Zd now close (RC-2a and RC-2b open) and the thyratron motor control is switched from normal speed potentiometer P-l to low-speed potentiometer P-2. The backward roll continues at a lower speed until limit switch LS-6 (Fig. 7) is closed by cam 75. Indexing switch 92 now moves to position 5 and a time delay relay winding TDW-1 is energized. During the delay interval introdueed by this relay, the cradle remains stopped at its backward limit. After a predetermined time interval, contacts TDC-l of the time relay close and the indexing switch now moves to position 6. Relay winding RW-7 is now energized and causes contacts RC-7a and RC-7b to close and motor 14 to run in its forward direction. Prior to reaching the forward limit, limit switch LS-5 is operated by cam 72' (Fig. 6) again switching the motor control to the low-speed potentiometer to slow down the roll of the cradle. When the forward limit is reached, limit switch LS-7 is closed and the indexing switch moves to position 7 where time delay relay winding TW-l is again placed in operation to introduce a delay interval before the indexing switch moves to position 8 to start the backward roll.

When the backward roll limit is reached the second time, the indexing switch moves to position 9 where a second time delay relay TDW2 is energized. The reason for another such relay is to be able to provide a difierent delay period when a limit is reached for the secondtime. This is desirable because the coating suspension may require a different time interval to flow to the edge of the reflector area after the area has once been wetted. The secondv forward roll occurs with the indexing switch in position 10.; the second time delay relay is again used in position. 11 when the forward roll limit is reached for thesecond time.

After, the delay interval upon reaching the forward limitfor the second time, the indexing switch moves from position 11 to position 12 whereuponrelay winding RW-6 is energized. to start the backward roll. When the cradle reaches approximately its vertical position, limit switch LS-S (Fig. 8) is energized and the indexing switch thereupon comes full circle and steps from position 12 back to position 1. In position 1, relay winding RW-3 is energized causing normally closed contact RC-3 in the holding circuit to open and terminate the cycle. Relay winding RW-8 is energized, causing the release of motor clutch 15 and the operation of centering cam valve V-S; the cradle is thereupon centered and locked in its vertical position as previously explained. At the same time, valve V-1 is de-energized, braking the vacuum and allowing the lamp envelope to be removed fromthe cradle and placed in a drier for drying the coating suspension.

The flow coating machine control system which has been described is adapted to rock the lamp envelope twice to each limit; that is, it provides two full backward and forward rolls. It will be appreciated that the system may readily be adapted to provide any desired number of rocking movement or rolls if greater evenness of reflective coating is desired, or in order to accommodate dilferent viscosities of coating suspension and different rates of drying thereof. Also the machine may readily be adapted for simultaneous processing of several short lamp envelopes, for instance four 24 inch envelopes, by appropriate disposition of the rubber O-tubing to allow vacuum pull down. Limit switches may be used to open the circuit of solenoid VW-4 and arrest the flow of coating suspension while the nozzles are passing over the gaps between adjacent lamp envelopes.

While the present invention has been described with particular reference to a specific preferred embodiment of same, the details of construction described are intended as exemplary and not in order to limit the invention thereto, except in so far as included in the appended claims.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A machine for applying a coating suspension. to a portion of the interior of a tubular envelope comprising a cradle pivotable on a horizontal axis for supporting said envelope so as to extend parallel to said axis, a reservoir for said coating suspension having an elongated projecting nozzle, means for translating the reservoir to cause the nozzle to penetrate the envelope, means for issuing coating suspension from said nozzle during movement thereof relative to the envelope in order to deposit a pool of coating suspension along the bottom of the envelope, and means for rocking said cradle on said axis through a prescribed angle less than 360 in order to spread said pool of coating suspension circumferentially into a band extending longitudinally through said envelope.

2. A machine for applying a coating suspension into a portion of the interior of a tubular envelope comprising a cradle for supporting said envelope horizontally, a reservoir for said coating suspension having an elongated projecting nozzle, means for translating the reservoir to cause the nozzle to penetrate the envelope, means for issuing coating suspension from said nozzle during movement thereof relative to the envelope in order to deposit a pool of coating suspension along the bottom of the envelope, and means for rocking said cradle between prescribed limits in order to spread said pool of coating suspension circumfcrentially in said envelope, including control means for reducing the rate of roll of the cradle on close approach to the limits and for holding the cradle stationary at the limits for a predetermined time interval.

3. A machine for applying a coating suspension to a portion of the interior of a tubular envelope comprising a cradle pivotable on a horizontal axis for supporting said envelope so as to extend parallel to said axis, a reservoir for said coating suspension having an elongated projecting nozzle. provided with a port at its end, means for circulating coating suspension to said port and bajclt to the reservoir to preventsettling thereof in the nozzle, means for translating the reservoir tocause the nozzle to penetrate the. envelope, means for opening the port in the nozzle during movement thereof relative to the envelope in order to deposit a pool of coating suspension along the bottom of the envelope, and means for rocking said cradle on said axis through a prescribed angle less than 360 in order to spread said pool of coating suspension circumferentially into a band extending longitudinally through said envelope.

4. A machine for applying a coating suspension to a portion of the interior of a tubular envelope comprising an elongated horizontally extending cradle pivotable on a horizontal axis for supporting said envelope so as to extend parallel to said axis, a reservoir for said coating suspension mounted on a carriage, means for translating said carriage horizontally along the axis of said cradle, an elongated nozzle projecting from said carriage along said axis and adapted to penetrate said lamp envelope, a port at the end of said nozzle, means for circulating said coating suspension to said port and back to the reservoir to prevent settling thereof in the nozzle, means for opening said port during movement of the nozzle relative to the envelope in order to deposit a pool of coating suspension along the bottom of the envelope, and means for rocking said cradle on said axis through a prescribed angle less than 360 in order to spread said pool of coating suspension circumferentially into a band extending longitudinally through said envelope.

5. A machine as in claim 4 including a pair of carriages each having a reservoir and projecting nozzle like that defined and adapted to penetrate the lamp envelope in unison from opposite ends.

6. A machine for applying a coating suspension to a portion of the interior of a tubular envelope comprising an elongated horizontally extending cradle for accommodating said envelope, resilient sealing material along the edges of said cradle forming a sealed space between envelope and cradle, a source of vacuum adapted to be connected to said sealed space to draw the envelope down into the cradle in order to correct any bowing of the envelope, a reservoir for said coating suspension having an elongated projecting nozzle, means for translating the reservoir to cause the nozzle to penetrate the envelope, means for issuing coating suspension from said nozzle during movement thereof relative to the envelope in order to deposit a pool of coating suspension along the bottom of the envelope, and means for rocking said cradle through a prescribed angle in order to spread said pool of coating suspension circumferentially in said envelope.

7. A machine for applying a coating suspension to a portion of the interior of a tubular envelope comprising an elongated horizontally extending cradle for accommodating said envelope, resilient sealing material along the edges of said cradle forming a sealed space between envelope and cradle, a horizontally journalled hollow shaft supporting said cradle and having a passageway therethrough communicating with said sealed space, valve means connecting a source of vacuum to said passageway for drawing the envelope down into the cradle in order to correct any bowing of the envelope during the application of coating suspension thereto, a reservoir for said cotaing suspension having an elongated projecting nozzle, means for translating the reservoir to cause the nozzle to penetrate the em'elope, means for issuing coating suspension from said nozzle during movement thereof relative to the envelope in order to deposit a pool of coating suspension along the bottom of the envelope, and means for rocking said hollow shaft through a prescribed angle in order to spread said pool of coating suspension circumferentially in said envelope.

8. A machine for applying a coating suspension to a portion of the interior of a tubular envelope comprising a l '10 l an elongated horizontally extending cradle pivotable on, a horizontal axis for supporting said envelope so asto extend parallel to said axis, a reservoir for said coating suspension mounted on a carriage, means for translating said carriage horizontally along the axis of said cradle, an elongated nozzle projecting from said carriage along said axis and adapted to penetrate 'said lamp envelope, said nozzle comprising an outer sleeve having a port at its end, an inner tube enclosed within said sleeve and leading back into said reservoir, an aperture in said inner tube near said port opening into the sleeve, a pump for circulating said coating suspension through the annular space between outer sleeve and inner tube to said port and back through said aperture and inner tube to the reservoir to prevent settling thereof in the nozzle, means for opening said port during movement of the nozzle relative to the envelope in order to deposit a pool of coating suspension along the bottom of the envelope, and means for rocking said cradle on said axis through a prescribed angle less than 360 in order to spread said pool of coating suspension circumferentially into a band extending longitudi nally through said envelope.

9. A machine for applying a coating suspension to a portion of the interior of a tubular envelope comprising an elongated horizontally extending cradle pivotable on a horizontal axis for supporting said envelope, so as to extend parallel to said axis, a reservoir for said coating suspension mounted on a carriage, means for translating said carriage horizontally along the axis of said cradle, an elongated nozzle projecting from said carriage along said axis and adapted to penetrate said lamp envelope, said nozzle comprising an outer sleeve having a port at its outer end, an inner tube enclosed within said sleeve and leading back into said reservoir, an aperture in said inner tube near said port opening into the sleeve, a pump for circulating said coating suspension through the annular space between outer sleeve and inner tube to said port and back through said aperture and inner tube to the reservoir to prevent settling thereof in the nozzle, said inner tube being slidable within said outer sleeve to open said port, a solenoid operated pneumatic cylinder displacing said inner tube in order to open said port during withdrawal of the nozzle from the envelope in order to deposit a pool of coating suspension along the bottom of the envelope, and means for rocking said cradle on said axis through a prescribed angle less than 360 in order to spread said pool of coating suspension circumferentially into a band extending longitudinally through said envelope.

10. A machine for applying a coating suspension to a portion of the interior of a tubular envelope comprising an elongated horizontally extending cradle for accommodating said envelope, resilient sealing material along the edges of said cradle forming a sealed space between envelope and cradle, a source of vacuum adapted to be connected to said sealed space to draw the envelope down into the cradle in order to correct any bowing of the envelope, a reservoir for said coating suspension mounted on a carriage, means for translating said carriage horizontally along the axis of said envelope, an elongated nozzle projecting from said carriage along said axis and adapted to penetrate said lamp envelope, said nozzle comprising an outer sleeve having a port at its end, an inner tube enclosed within said sleeve and leading back into said reservoir, an aperture in said inner tube near said port opening into the sleeve, a pump for circulating said coating suspension through the annular space between outer sleeve and inner tube to said port and back through said aperture and inner tube to the reservoir to prevent settling thereof in the nozzle, means for opening said port during movement of the nozzle relative to the envelope in order to deposit a poolof coating suspension along the bottom of the envelope, and means for rocking said cradle through a prescribed angle in order to spread said 11 12 9091 oi coating suspension circumferentially in. said References Cited in'the file of this patent envelope. H a

11. A machine as in claim 10 including control means UNITED STATES PATENTS for said cradle rocking means reducing the rate of roll Re. 24,187 Burwell July 31, 1956' of the cradle on close approach to the limits of said'pre- 5 1,913,757 Harmon June 13, 1933 scribed angle and holding the cradle stationary at the 2,133,015 Boylan eta1. Oct. 11', 1938' limits for a predetermined time interval. 

